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The #2 comment on this comments page (as of Feb 2015) is 9 years old and recommends phpass. I have independently security audited this product and, while it continues to be recommended for password security, it is actually insecure and should NOT be used. It hasn't seen any updates in years (still at v0.3) and there are more recent alternatives such as using the newer built-in PHP password_hash() function that are much better. Everyone, please take a few moments to confirm what I'm saying is accurate (i.e. review the phpass code for yourself) and then click the down arrow to sink the phpass comment to the bottom. You'll be increasing security across the Internet by doing so.

For those who want details: md5() with microtime() are a fallback position within the source code of phpass. Instead of terminating, it continues to execute code. The author's intentions of trying to work everywhere are admirable but, when it comes to application security, that stance actually backfires. The only correct answer in a security context is to terminate the application rather than fallback to a weak position that can potentially be exploited (usually by forcing that weaker position to happen).

To generate salt use mcrypt_create_iv() not mt_rand() because no matter how many times you call mt_rand() it will only have at most 32 bits of entropy. Which you will start seeing salt collisions after about 2^16 users. mt_rand() is seeded poorly so it should happen sooner.

As I understand it, blowfish is generally seen a secure hashing algorithm, even for enterprise use (correct me if I'm wrong). Because of this, I created functions to create and check secure password hashes using this algorithm, and using the (also deemed cryptographically secure) openssl_random_pseudo_bytes function to generate the salt.

<?php/* * Generate a secure hash for a given password. The cost is passed * to the blowfish algorithm. Check the PHP manual page for crypt to * find more information about this setting. */function generate_hash($password, $cost=11){/* To generate the salt, first generate enough random bytes. Because * base64 returns one character for each 6 bits, the we should generate * at least 22*6/8=16.5 bytes, so we generate 17. Then we get the first * 22 base64 characters */$salt=substr(base64_encode(openssl_random_pseudo_bytes(17)),0,22);/* As blowfish takes a salt with the alphabet ./A-Za-z0-9 we have to * replace any '+' in the base64 string with '.'. We don't have to do * anything about the '=', as this only occurs when the b64 string is * padded, which is always after the first 22 characters. */$salt=str_replace("+",".",$salt);/* Next, create a string that will be passed to crypt, containing all * of the settings, separated by dollar signs */$param='$'.implode('$',array("2y", //select the most secure version of blowfish (>=PHP 5.3.7)str_pad($cost,2,"0",STR_PAD_LEFT), //add the cost in two digits$salt //add the salt));

//now do the actual hashingreturn crypt($password,$param);}

/* * Check the password against a hash generated by the generate_hash * function. */function validate_pw($password, $hash){/* Regenerating the with an available hash as the options parameter should * produce the same hash if the same password is passed. */return crypt($password, $hash)==$hash;}?>

It is intended for use on systems where mt_getrandmax() == 2147483647.

The salt created will be 128 bits in length, padded to 132 bits and then expressed in 22 base64 characters. (CRYPT_BLOWFISH only uses 128 bits for the salt, even though there are 132 bits in 22 base64 characters. If you examine the CRYPT_BLOWFISH input and output, you can see that it ignores the last four bits on input, and sets them to zero on output.)

Note that the high-order bits of the four 32-bit dwords returned by mt_rand() will always be zero (since mt_getrandmax == 2^31), so only 124 of the 128 bits will be pseudorandom. I found that acceptable for my application.

The crypt() function cant handle plus signs correctly. So if for example you are using crypt in a login function, use urlencode on the password first to make sure that the login procedure can handle any character:

If you're stuck with CRYPT_EXT_DES, then you'll want to pick a number of iterations: the 2nd-5th characters of the "salt".

My experimentation suggests that the 5th character is the most significant. A '.' is a zero and 'Z' is the highest value. Using all dots will create an error: all passwords will be encrypted to the same value.

Here are some encryption timings (in seconds) that I obtained, with five different iteration counts over the same salt, and the same password, on a quad core 2.66GHz Intel Xeon machine.

I think a half a second is reasonable for an application, but for the back end authentication? I'm not so sure: there's a significant risk of overloading the back end if we're getting lots of authentication requests.